Various fluorochemicals have been used to impart water and oil repellency to a variety of substrates (for example, textiles, carpet, leather, paper, and non-woven webs). These fluorochemicals have most often been applied topically (for example, by spraying, padding, or finish bath immersion), but some fluorochemicals have also been useful as polymer melt additives for preparing water- and oil-repellent polymeric fibers, films, fabrics, etc. The resulting repellent substrates have found use in numerous applications where water and/or oil repellency characteristics have been valued.
For some applications, however, antistatic properties have also been necessary or desirable, particularly in combination with repellency.
Antistats or antistatic agents are used to dissipate electrostatic or static charge. Electrostatic charge build-up is responsible for a variety of problems in the processing and use of many industrial products and materials. Electrostatic charging can cause materials to stick together or to repel one another. This is a particular problem in fiber and textile processing. In addition, static charge build-up can cause objects to attract dirt and dust, thereby decreasing the effectiveness of fluorochemical repellents.
Sudden electrostatic discharges from insulating objects can also be a serious problem. With photographic film, these discharges can cause fogging and the appearance of artifacts. When flammable materials are present, a static electric discharge can serve as an ignition source, resulting in fires and/or explosions. Electrostatic charge is a particular problem in the electronics industry because modern electronic devices are extremely susceptible to permanent damage by electrostatic discharges. The build-up of electrostatic charge in insulating objects is especially common and problematic under conditions of low humidity and when liquids or solids move in contact with one another (tribocharging).
But conventional antistats (many of which are humectants that rely on the adsorption and conductivity of water for charge dissipation) have generally not been very effective in combination with fluorochemical repellents. The result of this combination has often been a substantial reduction or even elimination of either antistatic and/or repellency characteristics relative to the use of either additive alone.
Furthermore, it has been particularly difficult to combine conventional antistats and fluorochemical repellents in polymer melt processing applications, as, for example, the water associated with humectant antistats vaporizes rapidly at melt processing temperatures. This has resulted in the undesirable formation of bubbles in the polymer and has caused screw slippage in extrusion equipment. Many antistats have also lacked the requisite thermal stability, leading to the production of objectionable odors (for example, in melt blowing applications, where high extrusion temperatures are involved).
Thus, there remains a need in the art for antistatic agents and repellents that can be effectively combined to impart both good antistatic characteristics and good repellency characteristics to substrates in a cost effective manner and that, in particular, can be utilized as internal melt additives without suffering thermal decomposition, or causing processing problems or melt defects.